Note: Descriptions are shown in the official language in which they were submitted.
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PIPE REFRACTORY INSULATION
FOR FURNACES
BACKGROUND OF THE INVENTION
The invention relates generally to water-cooled members for supporting steel
slabs and
the like in reheating furnaces, and, more particularly, to refractory
insulation for such members.
In the processing of steel, ingots are robed into shapes such as slabs and
subsequently
reheated in furnaces for further rolling or other processing. Reheat furnaces
are typically
pusher furnaces, walking beam furnaces or a combination of the two. Each
features a series
of lengthwise supports, frequently called skid pipes or skids. These skids are
supported in an
elevated state by vertical supports so that both sides of the steel slabs may
be heated as they
travel through the furnace. The steel slabs are typically 9 to 10 inches
thick, 30 to 82 inches
wide and 30 to 40 feet long and are heated to final temperatures of
2100°F to 2500°F,
depending upon the type of steel and its intended use.
In pusher furnaces, the steel slabs are abutted front-to-back and slide along
the skids
as they are pushed through the furnace. As a fresh steel slab is introduced
into the input end
of the pusher furnace, a corresponding heated steel slab is extracted from the
discharge end for
rolling mill treatments or other processing. In contrast, a typical walking
beam furnace has a
number of fixed skids with "walking skids" positioned between them. The
walking skids are
equipped to rise upward, advance forward, withdraw downward and return to
their original
positions so that the steel slabs within the furnace are incrementally moved
forward. In both
pusher and walking beam furnaces, the top surfaces of the skids are equipped
with wear
castings, also known as "riders", that support the steel slabs.
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The skids and vertical supports in reheat furnaces must be compact in order to
leave
sufficient combustion space in the furnace chamber, must be strong enough to
support the
heavy steel slabs being treated and must be protected against injury by the
high temperatures.
As a result, hollow metal pipes through which cooling water is circulated are
typically used in
the construction of these components. If water-cooled pipes with bare outer
surfaces are used
for the skids and vertical supports, however, the absorption of heat through
the pipe metal to
the cooling water results in tremendous heat loss from the furnace. It is
therefore necessary
to insulate the pipes to minimize the heat loss.
Covering the pipes with insulation also protects them from damage due to the
high temperature
of the furnace.
Previous insulation systems have utilized preformed refractory members that
are welded
directly to the pipe. Examples of this type of insulation system may be found
in U.S. Patent
Nos. 3,647,194; 3,804,585; 4,070,151; 4,134,721 and 4,528,672. These
insulation systems
utilize members constructed of refractory material within which metal links,
coils or fasteners
are embedded. A portion of the metal link, coil or fastener is left exposed
through a hole in the
refractory material. Alternatively, the metal link, coil or fastener may
extend out of an end of
the member. The refractory members are sized so that they fit upon the pipe
being protected.
Once positioned on the pipe, the exposed portion of the metal link, coil or
fastener may be
welded directly to the surface of the pipe. While these insulation systems
have proven
effective, the movement of the heavy steel slabs during the heating process
causes the skids to
flex and vibrate. The impacts of the slabs also subject the skids to shocks.
The flexing,
vibration and shocks, along with the cyclical heating of the furnace to
extremely high
temperatures, results in occasional damage to the refractory members
necessitating their
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replacement. Replacement of the refractory members requires that the welds be
broken and the
remaining weld material ground off of the pipe surface. This is a time
consuming and labor
intensive process during which the furnace may not be operated. Furnace
downtime adversely
affects the profitability of the operation and must be minimized.
An alternative type of insulation system utilizes preformed refractory members
that
fasten together to cover pipes. Examples of these types of systems may be
found in U.S. Patent
Nos. 3,781,167; 4,182,609; 4,225,307; 4,312,385; 4,424,028 and 4,505,303. In
each of these
systems, the refractory members are cast so as to include fastening devices
such as tabs, clips
or hooks. The fastening devices join neighboring refractory members together
after they are
positioned upon the pipe. While these systems have also proven to be
effective, the
replacement of a single refractory memberrequires that neighboring members
also be removed,
or at least shifted. This is because each refractory member depends upon
neighboring
refractory members for support. This complicates the replacement process so
that the furnace
downtime increases. In addition, there is a greater chance of damage to
neighboring refractory
members.
U.S. Patent Nos. 3,941,160 and 4,228,826 disclose interlocking refractory
members for
covering and insulating pipes. More specifically, the refractory members are
shaped so that
they slide into engagement with one another as they are positioned on a pipe.
A disadvantage
of this arrangement is that, due to abutting neighbor members, a damaged
member must be cut
in order to be removed. This increases the complexity and time of the
replacement process.
A further disadvantage of many of the above insulation systems is that, by
utilizing
refractory members that are abutting or that are attached by their ends to the
pipe, they do not
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allow for thermal expansion of the refractory members. More specifically, when
heated to the extreme temperatures of a reheat furnace, the refractory members
may
expand against each other or the weld so that they crack.
Finally, U.S. Patent No. 3,820,947 discloses a fibrous ceramic insulating
blanket that is wrapped about a pipe and pressed over anchor studs that
project from
the pipe. A ceramic anchor is placed over each stud and secured by a nut so
that the
blanket is held in position against the pipe. The assembly is sprayed with a
liquid
which hardens to provide a relatively hard and erosion-resistant out-layer
over a
resilient inner-layer. A disadvantage of this construction is that it is
difficult to
replace a single section of the insulation even though only a small portion
may be
damaged.
Accordingly, it is an object of an aspect of the present invention to provide
a
pipe refractory insulation system wherein the refractory members may be
quickly
replaced.
It is another object of an aspect of the present invention to provide a pipe
refractory insulation system wherein the refractory members may be replaced
without
removing welds from the pipe.
It is another object of an aspect of the present invention to provide a pipe
refractory insulation system wherein a refractory member may be replaced
without
disturbing additional refractory members.
It is another object of an aspect of the present invention to provide a pipe
refractory insulation system wherein a refractory member may be replaced
without
being cut for removal.
It is still another object of an aspect of the present invention to provide a
pipe
refractory insulation system that accounts for thermal expansion of the
refractory
material.
It is still another object of an aspect of the present invention to provide a
pipe
refractory insulation system wherein a single section of the refractory
material may be
replaced.
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SUMMARY OF THE INVENTION
The present invention is directed to insulation, and a method of installing
same, for fluid-cooled pipes that support workpieces in a furnace such as the
type
used for reheating steel. A number of threaded studs are welded to opposing
surfaces
of a pipe or a web between a pair of pipes. A ceramic fiber blanket is then
placed
around the pipes. A pair of refractory members, each of which features an
aperture
sized to receive a stud, are placed over the pipes) and secured in place by
nuts
fastened to the studs.
While sized to cover a majority of the pipe surface(s), the refractory members
are mounted so that gaps exist between them. This allows room for the
refractory
members to thermally expand without breaking. In the situation where a skid
pipe is
being insulated, the gaps between the bottom edges of the refractory members
are
filled with blanket insulation. In contrast, the gaps between the top edges of
the
refractory members, which contain the wear castings, are filled with heat-
resistant
plastic. The remaining portions of the apertures are also filled with heat-
resistant
plastic.
Accordingly, in one aspect of the present invention there is provided a
thermal
insulation system for cladding a fluid-cooled pipe comprising:
a) a plurality of studs welded directly to an exterior surface of a length of
pipe to be insulated;
b) a plurality of preformed insulative refractory members adapted to
cover a majority of a circumference of the pipe, each refractory member having
an
elongated aperture completely therethrough through which one of said studs may
be
received;
c) a plurality of removable fasteners engaging said studs so that said
apertured refractory members are secured to said length of pipe and so that
said
apertured refractory members may slide parallel to a longitudinal axis of the
pipe
when said removable fasteners are loosened from said studs disposed through
the
apertures; and
d) a plurality of refractory members which interlock with one another
secured between the apertured refractory members thereby to cover a majority
of the
pipe surface, each of said interlocking refractory members featuring an "H"
shape so
CA 02308420 2003-11-26
as to engage and disengage neighboring refractory members above and below by
sliding parallel to the longitudinal axis of the pipe so that said refractory
members
may be removed without removing any fasteners from said studs.
The following detailed description of embodiments of the invention, taken in
conjunction with the appended claims and accompanying drawings, provide a more
complete understanding of the nature and scope of the invention.
Sa
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side elevational view showing a portion of a skid pipe and
vertical supports
therefor in a reheat furnace upon which an embodiment of the pipe refractory
insulation of the
invention has been installed;
Fig. 2 is a perspective view of the skid pipes of Fig. l illustrating the
installation of the
pipe refractory insulation;
Fig. 3 is a sectional view of the skid pipe of Fig. 1 taken along line 3-3;
Fig. 4 is a perspective view of the left vertical support of Fig. 1
illustrating the
installation of the pipe refractory insulation;
Fig. 5 is a sectional view of the vertical support of Fig. 4 taken along line
5-5 of Fig.
1;
Fig. 6 is a perspective view of the right vertical support of Fig. 1
illustrating the
installation of the pipe refractory insulation;
Fig. 7 is a sectional view of the vertical support of Fig. 6 taken along line
7-7 of Fig.
1;
Fig. 8 is a sectional view of the vertical support of Fig. b taken along line
8-8 of Fig.
1;
Fig. 9 is a side elevational view showing a portion of a skid pipe and a
vertical support
therefor in a reheat furnace upon which a second embodiment of the pipe
refractory insulation
of the invention has been installed;
Fig.10 is a perspective view of the skid pipe of Fig. 9 illustrating the
installation of the
pipe refractory insulation;
Fig. 11 is a sectional view of the skid pipe of Fig. 9 taken along line 11-11;
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Fig.12 is a perspective view of the vertical support of Fig. 9 illustrating
the installation
of the pipe refractory insulation;
Fig. 13 is a sectional view of the vertical support of Fig. 9 taken along line
13-13.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to Fig. 1, a skid pipe, indicated generally at 10, is shown
positioned
upon a dual-pipe vertical support, indicated generally at I2, and a single-
pipe vertical support
14. The structure is positioned within a pusher or walking beam repeat
furnace, the floor of
which is indicated at 15. The skid pipe is actually constructed of steel top
and bottom pipes
16 and 18 joined by a steel web 20. Similarly, the steel pipes 22 and 24 of
vertical support 12
are joined by steel web 26. The pipe of vertical support 14 is also
constructed of steel. While
the pipe refractory insulation of the present invention will be discussed
herein in terms of a
repeat furnace, it will be appreciated that many other similar environments,
such as an open
hearth furnace, require such insulation systems. Furthermore, while the
embodiments shown
herein disclose the insulation applied to pipes having a round cross section,
it is to be
understood that the invention may be applied to pipes having cross sections of
other shapes
(such as elliptical).
As may be seen from Fig. 1; the bottom pipe 18 of the skid pipe is connected
to the
pipes of vertical supports 12 and 14. The pipes of the vertical supports pass
into the floor 15
and are connected to a water source (not shown). As a result, water flows
through the pipes
of the vertical supports as well as bottom pipe 18 of the skid pipe. The top
pipe 16 of the skid
pipe is also connected to a water source so that water flows therethrough. As
a result, the skid
pipe 10 and the vertical supports 12 and 14 are cooled so that they retain
their strength under
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the extremely high temperatures of the reheat furnace (over 2400°F in
some instances). It
should be noted that the insulation of the invention could also be used to
cover pipes cooled
with an alternative fluid such as air.
A number of wear castings 28, also known as "riders", are attached in a spaced
relationship to the top of the top pipe 16 of the skid pipe. As a result, a
steel slab workpiece,
indicated in phantom at 29, is supported by the wear castings as it travels
through the furnace.
Typically, the wear castings are solid blocks of temperature resistant metal
such as chrome
alloys, nickel alloys and the like. The wear castings may be welded directly
to the pipe or, as
shown in Figs. 1 and 2, welded to a bracket 36 which is welded to the top of
the pipe.
Alternatively, as shown in Fig. 3, the wear casting 28 may be bolted to the
bracket 36 via bolt
38. Heat from the wear casting is withdrawn through the pipe 16, and into the
water flowing
therethrough, so that the wear casting does not lose its supportive strength.
To reduce the loss of heat from the furnace interior into pipes 16 and 18, and
the water
flowing therein, the skid pipe 10 is fitted with a number of refractory
members 30. Similarly,
vertical supports 12 and 14 are covered by refractory members 32 and 34. In
addition, the
refractory members protect the pipes from damage due to the high temperature
of the furnace.
The refractory members are preferably constructed of a high alumina castable
refractory.
The installation of the refractory members 30 upon skid pipe 10 will now be
explained
with reference to Figs. 2 and 3. A number of threaded studs 40 are first
welded to the web 20
of the skid pipe. The studs preferably are constructed of a heat-resistant
metal such as stainless
steel. A ceramic fiber blanket 44 is next placed over the studs 40 and 40' and
wrapped about
the pipes 16 and 18 and web 20. For reasons that will be explained, an excess
portion of the
blanket is left extending from bottom pipe 18 and top pipe 16. The blanket
provides an
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additional layer of insulation for the pipes and also provides shock
absorption for the refractory
members 30.
Each refractory member features arcuate portions 41 and 43 as well as an
aperture 46
that is sized to receive the threaded studs 40. Once the blanket 44 is wrapped
about the web
and pipes of the skid pipe, two refractory members are placed over opposing
studs 40 and 40'
and are secured in place via the engagement of nuts SO and 50' with studs 40
and 40',
respectively. While nuts SO and SO' (and washer 51) are illustrated, it should
be noted that
alternative removable fasteners may be used. The excess bottom portion of the
blanket fills the
gap 52 between the bottom edges of the refractory members 30 and 30'. Gap 52
allows the
refractory members to expand when heated without contacting one another so
that cracking
is avoided.
Heat-resistant plastic, such as is available from the Harbison-Walker company,
in
moldable (pliant or malleable) farm is pounded into place so that it covers
and fills the space
between the wear castings 28 and the refractory members 30 and 30', as
indicated at S8. The
excess top portion of the blanket 44 is placed adjacent to the base of wear
casting 28 to further
insulate it. insulating the top of the skid pipe in such a fashion provides a
number of
advantages. The refractory members 30 and 30' are protected from damage should
a wear
casting break. More specifically, should a wear casting such as 28 break, the
slab 29 (Fig. 1)
would come into contact with the plastic 58 before the refractory members 30
and 30'. In
addition, by surrounding the wear castings with plastic, their replacement is
greatly simplified
in that the bolts or welds securing them to the pipe may be more easily
accessed. Finally, the
plastic-filled gap 58 allows for the thermal expansion of members 30 and 30'.
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As indicated at 60, plastic is also used to fill in the remaining portion of
aperture 46 so
that nut 50 is protected from the heat of the furnace. The plastic 60 may also
be easily removed
so that nut 50 may be accessed.
The installation of refractory members 32 to dual-pipe support member 12 may
be
explained with reference to Figs. 4 and 5. Each refractory member 32 features
arcuate portions
71 and 73 and an aperture 70 that is sized to accommodate a threaded stud 72
that is welded
to the web 26 of vertical support 12. A ceramic fiber blanket 74 is placed
over the studs and
around the pipes and web of the vertical support with excess portions
extending from opposing
surfaces of pipes 22 and 24. Refractory members 32 and 32' are then placed
over the studs,
and support member 12, and are secured with nuts 76 and 76'. Heat-resistant
plastic is used
to fill the remaining portion of aperture 70. The excess portions of the
blanket 74 fill the gaps
80 and 82 between the refractory members 32 and 32'. Gaps 80 and 82 allow for
the thermal
expansion of the refractory members.
Figs. 6 through 8 illustrate the installation of refractory members 34 to
single-pipe
support 14. The refractory members feature an "H" shape so that they may
interlock and
support each others' weight upon placement about vertical support 14. As a
result, the
members 34 do not require studs or nuts to hold them in position.
Fastened refractory members such as 88 are positioned on the top and
incrementally
along vertical support 14. Each fastened refractory member features an
elongated aperture 90
that receives a threaded stud such as 92. The elongated slot allows the end
piece member 88
to be slid upwards, once nut 94 is loosened> so that a damaged member, such as
34', may be
raised and disengaged from supporting members for replacement. A lower
refractory member,
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such as the one indicated at 98, may be removed by loosening nuts 94 and 94'
and then raising
members 88, 88', 34 and 34'.
A ceramic fiber blanket 99 is loosely wrapped about pipe 14 prior to
installation of the
refractory members so that gaps such as 100, 101, 102 and 103 may be
insulated. As in the
previous installations, the gaps allow for thermal expansion of the refractory
members.
Referring back to Fig. 1, once refractory members 30, 32, 34 and 88 are
installed,
castable refractory material 106 and 108 is used to cover the junction between
the pipes of skid
pipe 10 and vertical supports 12 and 14.
Fig. 9 shows an embodiment of the pipe refractory insulation of the invention
installed
upon a structure that features a single pipe skid 110 supported by a dual-pipe
vertical support
112 that does not possess a web. As with the embodiment of Fig. 1, the pipes
122 and 124 of
the vertical support extend into the floor 115 of the furnace and receive
water from a source
(not shown). As a result, water flows through the pipes 122, 124 and 110 so
that they are
cooled and thereby retain their strength. Wear castings 128 for supporting
steel slab
workpieces are attached to the top of the skid pipe. The skid pipe is
insulated by refractory
members 130 while the vertical support is insulated by refractory members 132.
As illustrated in Figs. 10 and 11, a number of spaced threaded studs 140 are
welded to
skid pipe 110. A ceramic fiber blanket 144 is placed over the studs and around
the pipe with
excess portions at the top and bottom. The refractory members 130 and 130',
which feature
apertures 146 and 146', are then placed over the studs and are secured in
position with nuts 150
and 150'. The bottom excess portion of blanket may be used to fill gap 152,
which allows for
thermal expansion of the refractory members.
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As illustrated at 158, heat-resistant plastic is used to fill the space
between the top edges -
of the refractory members and surrounding the base of the wear casting. The
plastic is pounded
into the space as a pliant (or malleable) solid and then hardens. Heat-
resistant plastic is also
used to fill the remaining portions of apertures 146 and 146'.
As illustrated in Figs.12 and 13, refractory members 132 and 132', featuring
apertures
170 and 170', are attached to vertical support 112 via threaded studs 172 and
172' welded to
opposing surfaces of pipes 122 and 124. Nuts I76 and 176' secure the members
in position.
Prior to installation of the refractory members, ceramic fiber blanket
sections 174 and 174' are
placed over the studs and the opposing halves of pipes 122 and 124. Blanket
sections are also
used to fill the gaps between the refractory members as indicated at 180 and
182. The gaps
allows for thermal expansion of the refractory members.
After all of the refractory members are attached to the vertical support (as
illustrated
in Fig. 9), heat-resistant plastic, in pliant or malleable form, is pounded
into the top of the
vertical support. As a result, the plastic hardens so as to fill the space
between pipes 122 and
124, as illustrated at 185 in Fig. 13. The remaining portion of apertures 170
and 170' are also
filled with plastic.
As a final step, castable refractory material 206 (Fig. 9) is used to cover
the junction
between skid pipe 110 and vertical support 112.
In addition to the advantages already described, the installation of Figs. 1
and 9 allow
a damaged refractory member to be removed by simply removing the plastic from
its aperture
and unfastening a nut. A replacement refractory member may then simply be
secured in place
by a nut and washer. Furthermore, because each pipe section is covered by two
identical
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refractory member halves, only a few different types of refractory members
need to be kept in -
stock at the operation for maintenance purposes.
While the preferred embodiments of the invention have been shown and
described, it
will be apparent to those skilled in the art that changes and modifications
may be made therein
without departing from the spirit of the invention, the scope of which is
defined by the
appended claims.
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